ARCHIVED REPORTS_XR0002483 - Laserfiche WebLink

Home Browse Search

CLEARWATER GROUP Soil Vapor Extraction Test Field Procedures Purpose and Scope The purpose of the soil vapor extraction test is to evaluate the feasibility of contaminant volatilization in the vadose zone as a remedial option at the site, and determine the number of vapor extraction wells necessary In particular, the objectives of the test are to • Determine the effective radius of influence of a single well, • Determine the optimal vacuum and flow rates for a single well to obtain a significant radius of influence, and minimize the number of required wells, • Determine the air permeability of the vadose zone to evaluate the feasibility of volatilization for the given contaminant at the site, • Determine the number of required wells to remediate the site through volatilization in a reasonable period of time(<S years) Field Procedures and Equipment Soil Vapor Extraction Test Procgdures One to several different vapor wells or suitable monitoring wells are subjected to the vapor extraction test A monitoring well may be considered suitable for a vapor extraction test if at least five feet of well screen is exposed above the water table A vacuum source is attached to a given test well The soil vapor extraction test is conducted in several steps on the test well An initial step is conducted at a low vacuum and flow rate Subsequent steps consist of increasingly higher vacuum and flow rates until a maximum vacuum and flow rate is reached, as determined by equipment limitations or site geology During the test, vacuum is measured in surrounding monitoring points Monitoring points may be other vapor wells, vapor pomts or suitable monitoring wells Each step of the vapor extraction test is concluded on a test well when consecutive vacuum measurements from monitoring points differ by less than 0 1 inch water column within one-half to one hour Influent air samples, and if required by the local air quality authority effluent air samples,will be collected for appropriate analyses by a State- certified environmental laboratory The following data are collected during the pilot test • Vacuums at the test well • Vacuums in surrounding monitoring points Flow rates at the test well • Concentrations of volatiles in influent and effluent air streams • Per cent LEL and oxygen in influent air streams Soil Vapor Extraction Test Equil2me The vacuum source will be either an internal combustion engine (IC engine) with attached blower, or a 314 horsepower regenerative blower The IC engine is preferred for pilot tests due to the higher range of vacuums and flows that can be obtained, allowing a more realistic determination of the air flow conditions in the subsurface without the possible influence of equipment limitations Several manufacturers supply specially modified IC engines for the purpose of performing vapor extraction tests The IC engine with attached catalytic converter treats vapors prior to emission to the atmosphere If a regenerative blower is used, on-site electricity or a generator are used as a power source Carbon canisters can be attached to the regenerative blower to treat vapor emissions if necessary CLEARWATER GROUP(SVE TEST) 1 revised June 29, 2001